1. Field of the Invention
The invention lies in the field of automotive technology. More specifically, the invention relates to a method and a device for monitoring an internal combustion engine, in particular an internal combustion engine with direct injection of the fuel and/or extensive throttle-free load control.
A pertinent a prior art method for controlling an internal combustion engine is described in German published patent application DE 42 32 974 A1. There, a setpoint value of a torque which is to be set by means of the air mass flow rate is determined in a device for predefining the output torque. An estimated value of an ignition-angle-standardized actual torque is derived either from the measurement signal of a torque sensor or from the rate at which the air mass is aspirated into the combustion chambers. An ignition angle is adjusted as a function of the deviation between the setpoint value and the standardized estimated value of the torque. Unfortunately, torque sensors are still too expensive or not reliable enough for use in series-produced engines. On the other hand, determining the actual torque as a function of the sensed air mass flow rate supplies sufficiently precise values only for internal combustion engines which are controlled by means of the air mass flow rate.
2. Summary of the Invention
It is accordingly an object of the invention to provide a method and a device for monitoring an internal combustion engine, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which is operated with a high excess air factor of the air/fuel mixture and which method and device are reliable and simple.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method of monitoring an internal combustion engine, which comprises the following steps:
measuring an excess air factor with an oxygen probe arranged in an exhaust tract of an internal combustion engine; PA1 calculating an estimated value of an amount of fuel actually being metered into a cylinder per working cycle in dependence on the excess air factor determined by the oxygen probe; PA1 calculating an estimated value of an indicated torque of the internal combustion engine as a function of the estimated value of the amount of fuel; and PA1 actuating an emergency operating mode of the internal combustion engine if the estimated value of the indicated torque and a setpoint value of the indicated torque satisfy a predefined condition. PA1 measuring an excess air factor with an oxygen probe arranged in an exhaust tract of an internal combustion engine; PA1 calculating an estimated value of an amount of fuel actually being metered into a cylinder per working cycle in dependence on the excess air factor determined by the oxygen probe; PA1 actuating an emergency operating mode of the internal combustion engine if the estimated value and a setpoint value of the amount of fuel satisfy a predefined condition. PA1 a first device for calculating an estimated value of an amount of fuel being metered into a cylinder per working cycle, the estimated value of the amount of fuel being calculated as a function of an excess air factor determined by an oxygen probe in the exhaust tract of the internal combustion engine; PA1 a second device for calculating an estimated value of an indicated torque of the internal combustion engine as a function of the estimated value of the amount of fuel; and PA1 a third device for controlling an emergency operating mode of the internal combustion engine if the estimated value of the indicated torque and a setpoint value of the indicated torque fulfill a predefined condition.
The estimated value of the indicated torque can be calculated with a high level of quality because the actual amount of fuel is the deciding influencing variable for the value of the actual indicated torque.
The invention has the advantage that it monitors the fuel system which comprises the fuel pump and injection valves.
In accordance with an added feature of the invention, the excess air factor is corrected as a function of a secondary air mass flow rate.
In accordance with an additional feature of the invention, the estimated value of the indicated torque is additionally determined as a function of a mass flow rate into the cylinder.
In accordance with another feature of the invention, the setpoint value of the indicated torque is determined in dependence on a pedal value and a rotational speed of the internal combustion engine.
In accordance with a further feature of the invention, the predefined condition is a set difference between the estimated value and the setpoint value.
With the above and other objects in view there is also provided, in accordance with the invention, a method of monitoring an internal combustion engine, which comprises the following steps:
In accordance with again an added feature of the invention, the excess air factor is corrected as a function of a secondary air mass flow rate.
In accordance with again an additional feature of the invention, the predefined condition is considered satisfied if a difference between the estimated value and the setpoint value of the amount of fuel is greater than a predefined threshold value for longer than a predefined time period.
With the above and other objects in view there is provided, in accordance with an alternative of the invention, a device for monitoring an internal combustion engine of the type having an exhaust gas tract and an oxygen probe in the exhaust gas tract, the device comprising:
The first, second, and third devices may be embodied a separate functional units or individual program batches of a single processor.
It is advantageous for the estimated value of the amount of fuel is calculated as a function of an excess air factor which is determined by an oxygen probe arranged in the exhaust tract of the internal combustion engine. The excess air factor is a measured value with which the estimated value of the amount of fuel is calculated independently of a setpoint value of the amount of fuel.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method and device For monitoring an internal combustion engine, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.